trading is the best option, gambling is the worst 
Well everyone has the different experiences and few may like gambling and dislike trading, so it varies from person to person. Personally i find gambling to be a fun activity.
I will choose campaign. No money will be required to campaign and there is no risk. I earn good money by bounty. On the other hand, trading and gambling both are risky and capital required.
Campaigns are risk free but the amount of money from the campaign is very less. On the other hand if you do trading etc, you can earn a good lot of money in very short interval of time.